docs: def on_board(self, *args):
          """Draw myself for the first time as soon as I have the properties I
          need to do so.
  
          """
          if None in (
                  self.board,
                  self.origin,
                  self.destination
          ):
              Clock.schedule_once(self.on_board, 0)
              return
          self._trigger_repoint()